Rename constant names to match regular expressions and comply a naming convention

Author: JeanDeboutGat

webmagic-extension/src/main/java/us/codecraft/webmagic/configurable/ExpressionType.java

@@ -5,6 +5,6 @@
  */
 public enum ExpressionType {
 
-    XPath, Regex, Css, JsonPath;
+    X_PATH, REGEX, CSS, JSON_PATH;
 
 }

webmagic-extension/src/main/java/us/codecraft/webmagic/configurable/ExtractRule.java

@@ -77,21 +77,21 @@ public Selector getSelector() {
 
     private Selector compileSelector() {
         switch (expressionType) {
-            case Css:
+            case CSS:
                 if (expressionParams.length >= 1) {
                     return $(expressionValue, expressionParams[0]);
                 } else {
                     return $(expressionValue);
                 }
-            case XPath:
+            case X_PATH:
                 return xpath(expressionValue);
-            case Regex:
+            case REGEX:
                 if (expressionParams.length >= 1) {
                     return regex(expressionValue, Integer.parseInt(expressionParams[0]));
                 } else {
                     return regex(expressionValue);
                 }
-            case JsonPath:
+            case JSON_PATH:
                 return new JsonPathSelector(expressionValue);
             default:
                 return xpath(expressionValue);